I have a 99 Jeep Cherokee Sport that has a problem with the heater fan switch. It only works when it is on setting 4. If you turn it to 1, 2, or 3 the fan is not on at all. The guy who owned it previously said that he had replaced the switch itself but it didn't fix the problem. Does anyone know what could cause this?

There is a blower motor resistor on the 3 lower speeds. Not sure where you will find it but it will be on the heater housing so the air moving through the heater cools the coils of the resistors.

Could be the resistors have burnt out or the connector is loose somewhere.

JD

Does anyone know where this resistor is located at?

Ya the resistor sounds like your problem. It is found on the passenger side heater box in the coach. I think that it is held in with 2 screws. Easy fix 5 min.